Wafer carrier door and spring biased latching mechanism

ABSTRACT

A wafer container with a door, the door has at least one latching mechanism, wherein the latching mechanism has a spring member that holds the latching mechanism at one or more desired positions that preferably correspond to latch-open and latch-closed conditions. In a preferred embodiment, the spring member has an over-center condition that urges the latching mechanism towards the favored positions, thereby resisting unintended actuation of the latching mechanism. Moreover, in preferred embodiments, the latching mechanism has soft stops at the latch open or latch closed condition that minimizes abrupt snapping into position of the latching mechanism. Preferred embodiments utilize a rotatable member configured as a cammed member with an elongate rigid plastic member having at least one node, forming a plastic spring. The spring is pivotally mounted on the rotatable member and pivotally mounted to the door structure.

This application is a continuation of U.S. patent application Ser. No.10/318,374, now U.S. Pat. No. 6,880,718, which in turn claims thebenefit under 35 U.S.C. 119(e) of U.S. Provisional Application No.60/349,059 filed on Jan. 15, 2002.

BACKGROUND OF THE INVENTION

This invention relates to wafer carriers. More particularly it relatesto sealable wafer enclosures having doors with latching mechanisms.

Processing of semi-conductor wafers into finished electronic componentstypically requires many processing steps where the wafers must behandled and processed. The wafers are very valuable, and are extremelydelicate and easily damaged by physical and electrical shocks. Inaddition, successful processing requires the utmost in cleanliness, freeof particulates and other contaminants. As a result, specializedcontainers or carriers have been developed for use during processing,handling and transport of wafers. These containers protect the wafersfrom physical and electrical hazards, and are sealable to protect thewafers from contaminants. It is important that the containers remainsealed when in use to prevent damage to the wafers from contaminants. Itis also important from a process efficiency standpoint that carriers beeasily useable and cleanable.

Various configurations of door enclosures and latching mechanisms forsealable wafer carriers are known in the art. Some known latchingmechanisms use rotary members for actuating the latch, such as a cam. Aproblem, however, with such mechanisms is that the cam member canself-rotate at undesirable times. This self-rotation can causeunlatching of the door and exposure of the wafers to contaminants. Whenthe door is not in place on the carrier, self-rotation can causeextension of the latches, making it difficult to reinstall the door onthe carrier. Other latching mechanisms use systems of interlinkedlatching arms actuated by a rotary or sliding element. Such systems canhave similar problems with actuation of the latching mechanism atundesired times and by intended means.

Previous methods used with cam actuated latching mechanisms forrestraining cam rotation have typically involved a simple leaf springwith a bent tip arranged tangential to the cam. As the cam is rotatednear the rotational limit of travel where it is to be held, a surface orprojection of the cam slides past the bent tip of the leaf spring. Thecam is then held in position at a favored position by the spring forceof the leaf spring and friction between the parts. Such a mechanism doesnot generally urge or spring-bias the cam member toward the favoredposition to prevent further cam rotation should the cam be dislodgedfrom the detent. Moreover, if two favored positions are providedcorresponding to the latch-open and latch-closed position, two separateleaf springs are needed to adequately address both conditions. This addscomplexity to the mechanism and complicates assembly of the parts. Theleaf springs, if formed from plastic material, do not generally havesufficient rigidity in bending to generate enough friction to hold thecam in position. Alternatives, such as metallic materials, areundesirable in that sliding contact between such materials can generatedamaging particulates. Other known methods involve simple detentsystems, involving for example, projections from the cam member thatengage structures on the door. Such simple detents, however, can becomedisengaged at unintended times and by unintended means. Once a detent isdisengaged, the simple detent mechanism provides no biasing force urgingthe cam member back toward the detent to prevent latching or unlatchingof the door.

Accordingly, what is needed is a device or apparatus that providesfavored positions for a wafer carrier door latching mechanism, and thatalso provides some type of biasing force urging the latching mechanismtoward the favored positions to resist further movement of the latch inthe event it is dislodged from the favored positions.

SUMMARY OF THE INVENTION

A wafer container with a door having at least one latching mechanism,wherein the latching mechanism has a spring member that holds thelatching mechanism at one or more desired positions that preferablycorrespond to latch-open and latch-closed conditions. In a preferredembodiment, the spring member has an over-center condition that urgesthe latching mechanism towards the favored positions, thereby resistingunintended actuation of the latching mechanism. Moreover, in preferredembodiments, the latching mechanism has soft stops at the latch open orlatch closed condition that minimizes abrupt snapping into position ofthe latching mechanism. Preferred embodiments utilize a rotatable memberconfigured as a cammed member with an elongate rigid plastic memberhaving at least one node, forming a plastic spring. The spring ispivotally mounted on the rotatable member and pivotally mounted to thedoor structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wafer carrier with a machine interfaceon a piece of processing equipment;

FIG. 2 is a perspective view of a pair of latch assemblies of a wafercarrier door;

FIG. 3 is a view of a preferred embodiment of a latch assembly of awafer carrier door showing the latch in the open position;

FIG. 4 is a view of a preferred embodiment of a latch assembly of awafer carrier door showing the latch in the closed position;

FIG. 5 is a view of an alternative embodiment of a latch assembly of awafer carrier door;

FIG. 6 is a view of another alternative embodiment of a latch assemblyof a wafer carrier door;

FIG. 7 is a view of yet another alterative embodiment of the latchassembly of the wafer carrier door;

FIG. 8 is a perspective view of yet another embodiment of a latchassembly of a wafer carrier door;

FIG. 9 is a view of the embodiment of FIG. 8 showing the latch in anopen position;

FIG. 10 is a view of the embodiment of FIG. 8 showing the latch in aclosed position;

FIG. 11 is a view of yet another embodiment of a latch assembly of awafer carrier door with the latch in an open position;

FIG. 12 is a view of yet another embodiment of a latch assembly of awafer carrier door with the latch in a closed position; and

FIG. 13 is a view of yet another embodiment of a latch assembly of awafer carrier door.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a wafer carrier 20, is seated on automatedprocessing equipment 22. The wafer carrier comprises a container portion24 including a top 26, a bottom 28, a back 30, a pair of opposing sides32 and 34, and an open front 36. Inside the container portion 24 aresupports 38 for holding a plurality of horizontally aligned and spacedwafers. A machine interface 30 is attached to the exterior of the bottom28 of the container. Open front 36 is defined by a door frame 40 withlatch receptacles 42. The container portion 24 further has a roboticflange 44 on the top 26 of the container portion. A wafer carrier door46 fits into the door frame 40 to close the open front.

Referring to FIGS. 1–3, door 46 generally includes door chassis 48,latching mechanisms 50, 52, and mechanism covers 54, 56. FIG. 3 depictsa partial view of latching mechanism 50 in exemplary fashion. Themechanism shown has a rotary actuating member in the form of cam member68. Latching arms 58, 60, each have a cam follower portion 62, 64,respectively, engaged with the periphery 66 of cam member 68 at camportions 70, 72. As depicted in FIG. 3, each of latching arms 58, 60,has a latching portion 74, 76, at the end opposite from cam followerportions 62, 64. When key 78 is inserted into key slot 80 and rotated,cam follower portions 62, 64, slide along cam portions 70, 72. Due tothe shape of cam member 68, latching arms 58, 60, are translatedradially, extending or retracting latching portions 74, 76, throughlatch openings 82, 84. Latching portions 74, 76, are received by latchreceptacles 42 in the wafer carrier, allowing the door to be secured inplace. Mechanism covers 54, 56, serve to protect the latching mechanisms50, 52 from physical damage and contamination, and to serve as guidesfor latching arms 58, 60.

A preferred embodiment of the invention as shown in FIGS. 4 and 5. InFIG. 4, latching mechanism 50 is shown in the open position withlatching arms 58, 60, fully retracted. Spring member 86 is pivotallyattached to cam member 68 at pivot 88 and is also pivotally attached todoor chassis 48 at spring pivot 90. Spring member 86 restrains cammember 68 rotationally and is neutrally biased, exerting no biasingforce on cam member 68 in the position shown. Thus, spring member 86provides a favored position for latching mechanism 50 in this position.If cam member 68 is rotated clockwise, however, spring member 86 will bebiased in tension and will exert a steadily increasing biasing force ina counter-clockwise direction. This counter-clockwise biasing forceserves as a “soft” rotational stop for cam member 68 in the clockwiserotational direction from the favored position. If cam member 68 isrotated further in the clockwise direction, cam follower portions 62,64, eventually contact mechanical stops 92, 94, on cam member 68.

If cam member 68 is rotated counter-clockwise from the neutral positionas depicted, spring member 86 is biased in compression and initiallyexerts a steadily increasing rotational biasing force on cam member 68in a clockwise rotational direction. As cam member 68 is rotated furthercounter-clockwise and reaches the mid-point of its rotational travelrange, the biasing force of spring member 86 is directed through thecenter of cam member 68. In this position, spring member 86, althoughcompressed, exerts no rotational biasing force on cam member 68. As cammember 68 is further rotated in the counter-clockwise direction past themid-point of its rotational travel range, spring member 86 exerts abiasing force, now urging cam member 68 in the counter-clockwisedirection. As cam member 68 rotates further in the counter-clockwisedirection, the rotational biasing force exerted by spring member 86steadily decreases as spring member 86 decompresses. Once cam member 68reaches the fully latched position as depicted in FIG. 5, spring member86 once again reaches a neutral position and exerts no rotationalbiasing force in either direction. Thus, spring member 86 has anotherfavored position in this location. As before, if cam member 68 isrotated further counter-clockwise from this neutral position, springmember 86 is loaded in tension and exerts a steadily increasingrotational biasing force urging the cam member clockwise. Eventually, ascam member is turned further counter-clockwise, cam follower portions62, 64, contact mechanical stops 96, 98, on cam member 68.

The latching mechanism illustrated in FIGS. 3 and 4 has a number ofdistinct advantages. First, spring member 86 provides two favoredpositions for cam member 68 corresponding to the neutral positionsdescribed above. These favored positions are created with a singlespring member and without the need for sliding contact between partsthat can cause undesirable particulates. Secondly, spring member 86provides a rotational biasing force, urging cam member 68 toward eitherof the favored positions, depending on the rotational position of cammember 68. In operation, cam member 68 experiences about 90 degrees ofrotational travel range. Spring member 86 provides a rotational biasingforce over nearly the entire range, exerting no biasing force only whencam member 68 is at the mid-point of its rotational range, and when itis at either of the two favored positions. Thus the effective rotationalrange where spring member 86 provides a rotational biasing force urgingcam member 68 toward its favored positions is nearly 45 degrees in eachdirection. Finally, as explained above, spring member 86 provides abiasing force resisting rotation of cam member 68 beyond each of itsfavored positions. As a result, when cam member 68 is rotated to eitherof its favored positions, it is decelerated in a controlled fashion byspring member 86 as it moves past the favored position, and its momentumis absorbed. Once the momentum has been absorbed, spring member 86contracts, pulling cam member 68 to its favored position. The result isthat the favored positions are “soft”, and do not involve the collisionof mechanical parts, which can generate vibrations. Such vibrations areundesirable in that they can tend to “launch” any particulate matterpresent on the door or in the container, creating the possibility ofcontamination of the wafers. Another advantage of avoiding the collisionof mechanical parts as in “hard” favored positions is that suchcollisions can themselves generate undesirable particulates.

The material and geometry of spring member 86 may be selected so thatsufficient bias force is exerted to effectively prevent unintendedrotation of cam member 68, but is not excessive so as to unduly hinderintended rotation of cam member 68 when operated in use. In thepreferred embodiment of FIGS. 4 and 5, spring member 86 may be comprisedof thermoplastic material, but could be made from any compatibleresilient material suitable for use in a wafer container. The materialmay also be made electrically conductive if desired, for instance, bythe addition of carbon fiber fill, to provide electrical conductivityfor a grounding path.

It will be appreciated that, by varying the length, cross-section andmaterial used for spring member 86, it is possible to achieve a range ofthe amount of spring biasing force exerted by spring member 86. It ispreferable that the spring biasing force be effective for at least 5degrees of the rotational travel range of cam member 68 proximate toeach favored position, but a range of up to nearly 45 degrees of therotational travel range proximate to each favored position is possibleas described above in addition, although spring member 86 is depicted ashaving an arcuate shape, other geometries are possible and are withinthe scope of the invention, such as the s-shaped spring 100 of FIG. 6 orthe coil spring 102 of FIG. 6. Two or more spring members 104, 106, ofsmaller dimension may be used if desired, as depicted for example inFIG. 7. In addition, one or more torsion springs disposed within cammember 68 could be used to similar effect. Another embodiment of theinvention is depicted in FIGS. 9 and 10. In this embodiment, cam member68 has radial protuberance 108. Arcuate shaped spring member 110 ismounted to mechanism cover 54 at a point intermediate to tips 112 and114. Spring member 110 has a v-shaped bends 116, 118, proximate to tips112 and 114 respectively. Tips 112 and 114 are shaped conformingly toprotuberance 108. When mechanism cover 54 is installed on door chassis48, tips 112, 114, are proximate to the periphery 66 of cam member 68.When cam member 68 is at a position corresponding to a latch-closedcondition as shown in FIG. 10, protuberance 108 of cam member 68 isengaged and captured with tip 112, providing a favored position for cammember 68. Spring member 110 is not loaded and thus has a neutral biasin this position. As cam member 68 is rotated clockwise, v-shaped bend116 rides over protuberance 108, biasing spring member 110 in bending.The resilience of spring member 110 exerts a biasing force actingthrough v-shaped bend 116, tangential to protuberance 108. This biasingforce urges cam member 68 in a counter-clockwise direction, resistingthe clockwise rotation. As cam member 68 is rotated further clockwise,protuberance 108 clears v-shaped bend 116, and spring member 110 returnsto an unloaded condition.

Spring member 110 remains out of contact with cam member 68 and exertsno rotational biasing force on it until cam member 68 nears a positioncorresponding to a latch-open condition depicted in FIG. 9, andprotuberance 108 contacts v-shaped bend 118. As cam member 68 is rotatedfurther clockwise, v-shaped bend 118 rides over protuberance 108 againloading spring member 110 in bending. Once protuberance 108 clearsv-shaped bend 118, the resilience of spring member 110 acting throughv-shaped bend 118 urges cam member 68 clockwise. Protuberance 108 iscaptured and held by the shape of tip 114, constituting a favoredposition for cam member 68 corresponding to a latch-open condition.Spring member 110 once again has a neutral bias in this position. If cammember 68 is rotated further clockwise from this position, the distalend of tip 114 is pressed radially outward by protuberance 108, biasingspring member 110 in bending. Consequently, spring member 110 exerts abiasing force directed radially inward, increasing the sliding frictionbetween the distal end of tip 114 and radial protuberance 108. Thus, aforce resisting rotation of cam member 68 clockwise beyond the favoredposition is provided. If cam member 68 is rotated still furtherclockwise, cam follower portions 62 and 64 contact mechanical stops 92and 94 on cam member 68, but before the distal end of tip 114 clearsprotuberance 108.

In the embodiment shown in FIGS. 9 and 10, spring member 110 exerts abiasing force urging cam member 68 toward each of the two favoredpositions for a rotational range of cam member 68 of about 5–15 degreessurrounding favored position, thus resisting disengagement of the cammember 68 from the favored positions. In addition, this embodiment alsohas the advantage of “soft” favored positions, due to the biasing forceprovided by the distal end of tips 112 and 114 against protuberance 108as cam member 68 rotates in either direction past the favored positions.

In the embodiments shown in FIGS. 9 and 10, spring member 110 and cammember 68 are made from thermoplastic material, each preferably havingabrasion resistant qualities. As a person of skill in the art willappreciate, however, the scope of the invention includes members madefrom any suitable and compatible materials.

The latching arms themselves, rather than the rotating element of alatch assembly, may be provided with a spring bias toward favoredpositions, as shown for example in FIGS. 11–13. Although depicted with arotary actuating member, such an assembly would be particularly welladapted for a latch mechanism having no rotary actuating member, usingfor instance, a four bar linkage for actuation. Spring members 120, 122,in this embodiment of the invention function similarly to a Bellevilletype spring. Two favored positions are provided, corresponding to alatch-open and a latch-closed position. Spring member 120 is mountedbetween pivots 124, 126, and is attached to latching arm 58 at centerpivot 128. Similarly, spring member 122 is mounted between pivots 130,132, and is attached to latching arm 60 at center pivot 134. Each ofspring members 120, 122, is normally straight, but slightly longer thanthe distance between the pivots to which it is attached. Thus, springmembers 120, 122, take on a slightly arcuate shape when installedbetween the pivots and with no load applied as shown in FIGS. 11 and 12.When cam member 68 is rotated counter-clockwise from the latch-opendetent position shown in FIG. 11, latching arms 58, 60, are translatedradially outward along the longitudinal axis of each latching arm,causing center pivots 128, 134, to also move radially outward. Springmembers 120, 122, are consequently loaded in compression, and exert aforce acting through center pivots 128, 134, resisting the radialmovement of latching arms 58, 60. When center pivot 128 reaches a pointon a line directly between pivots 124, 126, and center pivot 134 reachesa point on a line directly between pivots 130, 132, each spring member120, 122, is fully compressed and exerts no radial biasing force onlatching arms 58, 60.

When cam member 68 is rotated further counter-clockwise so that centerpivots 128, 134, move further radially outward, spring members 120, 122,begin to decompress and exert a force directed radially outward, urginglatching arms 58, 60, toward the latch-closed detent position depictedin FIG. 12. When latching arms 58, 60, are fully extended as shown inFIG. 12, spring members 120, 122, are once again in a neutral position,exerting no biasing force on latching arms 58, 60.

It will be appreciated that, by varying the length, cross-section andmaterial used for spring members 120, 122, it is possible to achieve arange of the amount of spring biasing force exerted by spring members120, 122, It is preferable that the spring biasing force is effectivefor at least 10% of the longitudinal travel range of the latching armsproximate to each favored position, but a range up to nearly 50% of thelongitudinal travel range proximate to each favored position ispossible.

Another embodiment wherein a biasing force is provided directly to thelatching arms using a spring arrangement having a single pivot on thedoor chassis is illustrated in FIG. 13. Those of skill in the art willrecognize that many other such variations are possible and are withinthe scope of the invention.

Additional objects, advantages, and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims. Although the description above contains manyspecificities, these should not be construed as limiting the scope ofthe invention but as merely providing illustrations of some of thepresently preferred embodiments of the invention. Thus, the scope of theinvention should be determined by the appended claims and their legalequivalents, rather than by the examples given.

1. A wafer container, comprising: a container portion including a top, abottom, a pair of opposing sides, a back and an open front: a pair ofwafer supports in the container portion for holding a plurality ofhorizontally aligned and spaced wafers; and a door to sealingly closethe open front, the door comprising: a door chassis; at least onelatching mechanism on the door chassis, said at least one latchingmechanism having a rotary actuating member presenting a radialprotuberance; and at least a first spring member operably coupled withthe door chassis, said spring member having structure for engaging theradial protuberance of the rotary actuating member to hold the rotaryactuating member at a first favored position, said spring member adaptedto urge said rotary actuating member toward the first favored positionover a first rotational range of said rotary actuating member of atleast 5 degrees proximate to the first favored position.
 2. The wafercontainer of claim 1, wherein said spring member is neutrally biasedwhen said rotary actuating member is at the first favored position. 3.The wafer container of claim 1, wherein the rotary actuating memberpresents a second radial protuberance, and wherein the spring memberfurther comprises structure for engaging the second radial protuberanceto hold the rotary actuating member at a second favored position, thespring member arranged so as to urge said rotary actuating member towardthe second favored position over a second rotational range of saidrotary actuating member of at least 5 degrees proximate to the secondfavored position.
 4. The wafer container of claim 3, wherein said springmember is neutrally biased when said rotary actuating member is at thesecond favored position.
 5. The wafer container of claim 1, wherein saidspring member has an arcuate shape.